fps wrong with codecpar

[ggarra13]

Summary of the bug:

Compiling and running doc/examples/muxing.c (which has codecpar changes) results in a movie with wrong fps (25.10) instead of 25.

How to reproduce:

% muxing test.mov
(snip)
pts:440320 pts_time:9.98458 dts:440320 dts_time:9.98458 duration:1024 duration_time:0.02322 stream_index:1
[libx264 @ 0xc26780] frame I:21    Avg QP: 5.56  size:  4421
[libx264 @ 0xc26780] frame P:229   Avg QP: 4.77  size:   790
[libx264 @ 0xc26780] mb I  I16..4: 79.5% 12.9%  7.7%
[libx264 @ 0xc26780] mb P  I16..4: 66.2%  0.5%  0.1%  P16..4: 32.7%  0.3%  0.2%  0.0%  0.0%    skip: 0.0%
[libx264 @ 0xc26780] final ratefactor: 0.68
[libx264 @ 0xc26780] 8x8 transform intra:2.2% inter:49.3%
[libx264 @ 0xc26780] coded y,uvDC,uvAC intra: 2.5% 11.2% 7.7% inter: 1.2% 100.0% 3.1%
[libx264 @ 0xc26780] i16 v,h,dc,p:  0%  0%  0% 100%
[libx264 @ 0xc26780] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 14% 28%  7% 51%  0%  0%  0%  0%  0%
[libx264 @ 0xc26780] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 14%  4%  5% 70%  4%  0%  0%  2%  1%
[libx264 @ 0xc26780] i8c dc,h,v,p:  0%  4%  4% 91%
[libx264 @ 0xc26780] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0xc26780] ref P L0: 98.3%  1.0%  0.5%  0.3%
[libx264 @ 0xc26780] kb/s:218.92
[aac @ 0xc27c80] Qavg: 363.339

% ffprobe test.mov
ffprobe version N-80655-gc60bf7f Copyright (c) 2007-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  configuration: --enable-gpl --enable-shared --enable-gray --enable-runtime-cpudetect --enable-bzlib --enable-libfreetype --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libass --enable-libvpx --enable-libx264 --enable-zlib
  libavutil      55. 26.100 / 55. 26.100
  libavcodec     57. 46.100 / 57. 46.100
  libavformat    57. 40.101 / 57. 40.101
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.102 /  6. 46.102
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mov':
  Metadata:
    major_brand     : qt  
    minor_version   : 512
    compatible_brands: qt  
    encoder         : Lavf57.40.101
  Duration: 00:00:10.03, start: 0.000000, bitrate: 289 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 352x288, 220 kb/s, 25.10 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 64 kb/s (default)
    Metadata:
      handler_name    : DataHandler